The marine midge Clunio marinus lives in the rocky intertidal zone of the European Atlantic coast. The insect has synchronised its life cycle with the rhythm of the tides: Adults live only for a few hours and adult emergence and reproduction only take place when the water is as low as possible. These occasions recur predictably during the low tides of spring tide days, around new moon and full moon. Hence, development of Clunio is tightly regulated by a so-called "circalunar clock". This biological timekeeping mechanism ensures that Clunio adults are only ready to emerge during a few days around the spring tides. Additionally, daily emergence time is controlled by a circadian clock, ensuring the midges only emerge short before the time of low tide.
In the laboratory, Clunio's lunar rhythm of adult emergence continues for several months in the absence of any cues on the external lunar cycle. This experiment underlines that the rhythm is controlled by timekeeping mechanism endogenous to the insect - the circalunar clock. Now classic behavioural experiments by Dietrich Neumann and his coworkers revealed some of the basic properties of the circalunar clock, for example how it can be reset by moonlight. But despite the fact that circalunar clocks are very common in marine organisms, their molecular basis is to date still entirely unknown. The recently published Clunio marinus reference genome now finally allows to take studies in Clunio to the molecular level, possibly allowing to uncover the first molecular components of circalunar clocks.
Research on the circalunar clock of Clunio marinus is carried out by the Max Planck Research Group "Biological Clocks" at the Max Planck Institute for Evolutionary Biology. Further information can be obtained from their webpage or from Tobias Kaiser.